Patent GB-191301157-A (GB)
Title: Improvements in Switches for Automatic Telephone Systems.
Inventor: WILLIAM MANSFIELD BRUCE
IPC: H01H67/06
Filed: 1913-01-15
Abstract: 1157. Bruce, W. M. Jan. 26, 1912, [Convention date]. Void. [Published under Section 91 of the Act.] Automatic exchange systems and apparatus. -A selector having a capacity of 100 lines, and operated as usual by two sets of impulses, corresponding to the tens and units digits of the wanted line, has its terminals arranged in two levels of fifty sets each, the upper and lower levels being engaged by separate sets of rotatable wipers. The first series of impulses operates a long-step ratchet magnet, which moves the wipers over five terminals at a time, and at the conclusion of the series a relay which puts in circuit either the upper or the lower set of wipers is energized or left unenergized according to whether an even or odd number of steps has been taken. A group of ten lines having been selected in this way, the second series of controlling-impulses then operates a short-step ratchet magnet to move the wipers from one terminal to the next until the selected wipers are on the wanted line. The arrangement of the terminals with the lower sets displaced five points to the right, is shown in Fig. 7. The bottom row, of which every tenth terminal is grounded, the rest being omissible, is engaged by an auxiliary or seventh wiper in the circuit of the wiperchoosing relay. To select the No. 12 set of terminals, three impulses would first be sent to operate the long-step magnet, which moves the wipers to the position 3<1>. This position does not include a grounded terminal in the seventh row so that the wiper-choosing relay, which is now connected to the seventh wiper, remains de-energized and leaves the upper set of wipers connected to the incoming line. Two impulses are then sent to operate the short-step magnet to bring the wipers to the No. 12 terminals. If it had been desired to select the No. 57 terminals, which are immediately below No. 12, sets of two and seven impulses would have been sent. The long-step magnet would have brought the wipers to the position 2, and in this position the wiper-choosing relay would have become energized over the grounded seventh terminal, with the result that the lower set of wipers would have been connected in place of the upper. The succeeding seven impulses would then have brought the wipers to the No. 57 terminals. The out-going lines from the bank terminals may be numbered to correspond with the impulses that are required for selecting them. Construction of selector. When the long-step magnet 1, Fig. 4, is energized, a pawl a', normally held out of action by a tail-piece a<3>, engages a ratchet a to drive the wiper-shaft 5. Overdrive is prevented by a projection a<6> on the armature - lever engaging a reverse ratchet a<8>. The short-step magnet 2 operates through an arm b<2> and pawl b<1> on a smallertoothed ratchet b. The release magnet 3 has an armature with extensions b', b<8> for withdrawing the pawl b<1> and detent b<10> to allow a spring to return the shaft 5 to its normal position. Circuit arrangements. The selection is controlled by current-interruptions in the line a, a<1>, the circuits being shifted at the termination of each series by a three-position auxiliary switch J, controlled by a magnet E. As soon as connexion is made to the selector, a line-relay A is energized and closes a circuit through a slow-acting release relay B, which remains energized throughout the connexion. At each current-interruption in the line a, a<1>, the circuit of the long-step magnet mm<1> is closed through a back-contact of the relay A, a front-contact of the relay B, a back-contact of the testrelay H, and the arm 22 of the auxiliary switch J. A slow-acting relay C is energized in a branch of this circuit and closes the circuit of a ringing-relay D, the energization of which is without effect at this stage. At the end of the series of impulses, the relay C de-energizes, and closes a circuit for the magnet E from the off-normal ground-contact 36. The magnet E momentarily connects the wiper-choosing relay G to the seventh wiper 27 and moves the auxiliary switch J to its second position. If the seventh wiper is on a grounded terminal the relay G energizes, locking itself up and preparing for the ultimate establishment of a connexion between the wires 64, 65 and the lower wipers 62, 63. Otherwise the connexion to the upper wipers 60, 61 remains unshifted. The switch J being in its second position, the second series of interruptions operates the short-step magnet mm<2> to complete the adjustment of the wipers, and if the wanted line is idle the magnet E is then energized as before and moves the switch J to its third position, completing the connexion of the wires 64, 65 to the wipers 60, 61 or 62, 63. Supply of ringing- current. The calling subscriber now operates his impulse-sender a number of times to energize the relay C, which closes the circuit of the slow release ringing-relay D, which connects a ring- ing - generator to the selected line. When the called subscriber replies, he is supplied with microphone current through the windings of the back-bridge relay A'. Release. When both subscribers have hung up their receivers, a circuit for the release magnet R is closed through the off-normal contact 95 and backcontacts of the relays A', B, A. A magnet R' in a branch of this circuit releases the auxiliary switch J, and a second branch circuit leads to the trunk-wire a<2> to release the preceding selectors. If the calling subscriber should hang up his receiver before the called subscriber, the r e l a y C i s momentarily energized, and the trunk-wire a<2> is connected to ground over a front-contact of the relay C and a back-contact of the relay B. The preceding selectors are therefore at once released, but the final selector is only released when the called subscriber hangs up. Busy test and signal. At the conclusion of the second series of setting-impulses, in the momentary interval between the de-energization of the relays C, D, a test-relay H is connected over the switch-arm 78 to the test-wiper 73 or 73<a>. If this wiper rests on a grounded test-terminal, the wanted line being busy, the relay H locks itself up and connects a tonesignal to the calling line, at the same time opening the circuits of the magnets E, mm<2> to lock the switch J in its second position and to prevent the wipers from being moved on to other terminals in case the calling subscriber should operate his impulse-sender to ring the desired subscriber.